1. Field of the Invention
This invention pertains to nuclear reactor handling apparatus and more particularly to an arrangement for handling a radioactive fuel assembly during dry transfer operations at a reactor site.
2. Description of the Prior Art
In today's commercial nuclear power plants, there exists a requirement to replace the nuclear core at predetermined time intervals, usually on the order of once every year. This involves removal of irradiated fuel assemblies from the core which is located within a reactor vessel, and after an appropriate period of storage in a spent fuel pit, transferring the fuel assemblies from the storage pile into a shipping cask. Since the cask is designed to function additionally as a radiation shield, the cask may be handled with complete safety and without the need for specialized radiation protection equipment. The shipping cask with the irradiated fuel assembly contained within it is sealed and then loaded a truck and shipped off the nuclear reactor site. It is to be noted, that throughout these transfer operations, the irradiated fuel assembly is shielded at all times. The operations whereby the fuel assembly is removed the core and transferred into the shipping cask are all performed underwater which serves as a radiation shield; thereafter, the shipping cask itself serves as a radiation shield.
In the prior art, replacement of the spent fuel assemblies by new fuel assemblies did not usually require the above mentioned radiation protection procedures. This was because new fuel assemblies such as those utilized in boiling water reactors or pressurized water reactors contain enriched uranium oxide which is not radioactive. Therefore, in the prior art, new fuel elements were brought onto the reactor site by truck or rail, were removed therefrom by a crane and then transferred to a new fuel storage pit without being shielded during these operations.
With the increasing availability of fissile Plutonium 239, which is produced as a by-product within water moderated nuclear reactors, and the inherent economic advantages offered by the use of this nuclear fuel, it is certain that new fuel assemblies will contain significant amounts of recycled Plutonium 239. Since this material is highly radioactive in its "natural state," the prior art handling techniques for a new fuel assembly is no longer satisfactory. That is, that all handling operations for new fuel assemblies containing Plutonium 239 must be performed with the fuel assembly being adequately shielded to prevent site personnel from being exposed to highly dangerous radioactivity.